The proposed project is a radiotracking study of social organization in an unrestrained population of the southern flying squirrel, Glaucomys volans. Our goal is to test certain hypotheses about the selective advantage of this species' social organization, and ultimately to gain insight into the adequacy of classical Darwinian selection acting on the individual, as opposed to group or kinship selection schemes, for explaining social organization. In this species, adult females are territorial, while adult males are socially tolerant. Specific hypotheses to be examined are that female territoriality carries the selective advantage of assured access to tree nest cavities needed for raising young, and that males compete for access to females through a mechanism that improves the mating frequency of successful males more than would territoriality. Failure of the second hypothesis would raise questions about the adequacy of individual selection for fully explaining the social structure of this species. Our basic technique will be to attach miniature radio transmitters to live-trapped squirrels, and to track their movements with directional receiveing antennas after they have been released again into the wild. This will enable us to establish such information as home range size, social interaction, nest cavity utilization, patterns of movements, and rates of movements. The results of this study will take on added value through comparison with studies of other species in the squirrel family Sciuridae. The great variability of social structure in this widely distributed group makes it an ideal one in which to study the adaptive significance of social structure.